Giant magnetocaloric effect of thin Ho films

We report a theoretical study of the impact of finite size on the magnetocaloric effect (MCE) of thin Ho films. For strong external field strengths, the adiabatic temperature change Delta T-ad is comparable to the value found in bulk Ho, reaching about 12 K for an external field strength change Delta H = 50 kOe. For thicknesses below the helix period, there is a large enhancement. In this thickness range, the helical state does not form, leading to a giant MCE reaching Delta T/Delta H = 6.5 K/T for Delta H = 2 kOe. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549566]